Generally, a heat treatment process for controlling a heating or cooling rate is performed to improve characteristics of a metal product. Quenching is referred to a process of quickly cooling down a metal product, which is heated to a high temperature by heat treatment, to cause its metal structure undergo a phase change. The quenching process is performed by spraying a coolant such as oil onto the surface of the metal product.
Korean Patent Publication No. 10-2016-0041996 (published on Jun. 18, 2018) proposes a device for spraying coolant as a quenching system for heat treatment metal products.
This system discloses a conical nozzle. An outer ring and an inner ring are engaged with each other to form an inclined inner engagement surface. An opening is formed in the inclined inner engagement surface through which the product passes.
Further, at least one quenching ring is provided to adjust a distance between the outer ring and the inner ring using a fastener. Due to such adjustment, a shape and a size of the nozzle can change, thereby adjusting a flow rate of the coolant sprayed out.
A ring plenum is formed in the quenching ring to receive the coolant supplied from the outside. The nozzles are connected to the ring plenum. In the conventional quenching system, the coolant is injected into the nozzles at the same pressure with each other regardless of the location of nozzles. That is, injection pressure of the coolant is the same regardless of the location of nozzles.
However, the pressures of the coolant sprayed out are different from each other depending on the location of the nozzles due to the influence of gravity. For example, a nozzle located at the top of the ring plenum is different from a nozzle located at the bottom of the ring plenum in the spray pressures of the coolant. Due to such difference, the surface of the metal product is quenched uniformly.
Furthermore, the nozzles are integrated with the quenching ring to form a single body. Thus, it is impossible to adjust a spraying angle of the coolant.
The conventional method adjusts the interval between the outer ring and the inner ring using the fastener and control the amount of the coolant sprayed out. However, it is difficult to precisely control the injection amount of the coolant with such method. Thus, there is a limitation in controlling the cooling rate of the product. For related conventional art, see Korean Patent Publication No. 10-2016-0041996 (published on Apr. 18, 2016).